Process for electrostatic dressing and/or working up of salt and mineral mixtures

ABSTRACT

Process in which raw or crude salt and mineral mixture are intensively mixed with an aliphatic, unbranched fatty acid having a chain length of three to 18 carbon atoms or with an aromatic carboxylic acid or with mixtures of said aliphatic and aromatic acids and an ammonium salt of a lower aliphatic acid, and thereafter treated with air having a relative humidity of 5 to 40 percent in an electrostatic separation zone at a temperature of about 15* to about 40* C.

United States Patent [191 Fricke et al.

[ Apr. 9, 1974 PROCESS FOR ELECTROSTATIC DRESSING AND/0R WORKING UP 0F SALT AND MINERAL MIXTURES Inventors: Gunter Fricke, Neuhof; Arno Singewald, Kassel, both of Germany Assignee: Wintershall Akti engesellschaft,

Kassel, Germany Filed: Apr. 23, 1973 Appl. No.: 353,718

Related US. Application Data Continuation of Ser. No. 31,030, March 26, 1970,

' abandoned.

Us. Cl. 209/9, 209/127 Int. Cl B03b 1/04 Field of Search 209/4, 9, 11, 127

v References Cited UNITED STATES PATENTS 6/1968 Peuschel 209/9 11/1969 Frickeetal .(209/9 l/1963 Autenrieth et 51.; 209/127 Primary Exa'miner-Frar1k W. Lutter' Assistant Examiner-William Chuchlinski, Jr. Attorney, Agent, or Firm-Michael S. Striker [57] ABSTRACT Process in which raw or-crude saltand mineral mixture are intensively mixed with an aliphatic, unbranched fatty acid having a chain length of three to 18 carbon atoms or with an aromatic carboxylic acid or with mixtures of said aliphatic and aromatic acids and an ammonium salt of a lower aliphatic acid, and thereafter treated with air having a relative humidity of 5 to 40 percent in an electrostatic separation zone at a temperature of about 15 to about 40 C.

7 Claims, NO Drawings 1 PROCESS FOR ELECTROSTATIC DRESSING AND/OR WORKING UP OF SALT AND MINERAL MIXTURES This is a continuation, of application Ser. No. 31,030,

filed Mar. 26, 1970 now abandoned. The process is particularly suitable for separating Kieserite from crude salt mixtures obtained in the potassium industry, separating a carbonate, as for instance MgCO and/or an oxide or fluoride, as for instance CaF, from various mineral and salt'mixtures containing the same.

This invention relates to a process of dressing and/or workin g up mineral and salt mixtures for the separation of certain components therefrom.

Kieserite (MgSO -H O) occurs in natural potassium salt mineral deposits associated with Sylvanite and rock salts as a main orsecondary component thereof. Kieserite occurs as the main mineral component in hard salts. In the processing of minerals for obtaining potassium therefrom, kieserite is recovered with the rock salt in the residues, i.e., in the form of a potassium poor residue following separation of the potassium.

For separating the kieserite from the potassium residues, many processes are known. For example, it has been proposed that crude kieserite be purified, that is, that the kieserite be separated from the accompanying substances through multi-stage washing and filtering In German Pat. No. 1,078,961, an electrostatic process for the preparation of kieserite is described, ac-

cording to which each ton of the material to be worked up is treated with 100g to 600g 2,4-dichlorophenoxy acetate and then electrostatically separated at a temperature of above 120C.

This process has the disadvantage that it requires considerable amounts of an expensive chemical compoundand also makes necessary the use of high temperatures. Further in this process there must be observed a definite order or sequence of separating the component materials. The presence of 2,4- dichlorophenoxy acetate exerts an inhibitory effect'on the following electrostatic separation of rock salt (Sylvanite). The recovery of both components is only possible with this process, if first the Sylvanite is separated with the aid of a KCl selective additive and if then the kieserite is recovered by means of 2,4-dichlorophenoxy acetate from the Sylvanite residue. This type of process requires-in all cases large amounts of the conditioning agent. Further, the duplicated steps of conditioning and separating gives rise to considerable technical expense which contributes considerably against any widespread acceptance of the process.

In Auslegeschrift 1,261,453 (US. Pat. Application Ser. No. 651,653), an electrostatic process is described which is characterized in that the materials to be dressed are treated with highly dispersed water adsorption agents and'fatty acids and in that the mixture is warmed with air having a relative humidity of, for example, 3 to 10 percent. The separation temperatures used in this process amount to about 40 to C.

The object of this invention is to provide an economically feasible and simple process for separating salt and mineral mixtures into their various components.

Another object is to provide a process for separating mineral and salt mixtures, such as the crude saltmixtures obtained in the potassium industry, liquid'spar, carbonate, fluoride and oxide mixtures, into their components by electrostatic means.

Still another object is to provide such a process utilizing for the electrostatic separation, air having a relative humidity of 5 to 40 percent and low temperatures ranging from about 15 to 40C. I

These and other objects and advantages will become apparent fromthe following description.

The process is particularly suitable for use in the working of the crude salt mixtures obtained in the potassium industry, for instance hard salts or kieserite resworking of other mineral and salt mixtures such as for recoveringMgCO from carbonate mixtures, for recovering an oxide or fluoride such as CaF from mixtures containing the same.

In carrying out the process of the invention, the material to be worked up is intensively mixed with a) an aliphatic, unbranched fatty acid having a chain length of three to 18 carbon atoms and preferably five to 12 carbon atoms, or with b) an aromatic carboxylic acid, or with c) a mixture of an aliphatic and aromatic acid or any of (a), (b), or (c) with an ammonium salt of a lower aliphatic acid and preferably ammonium formiate or ammonium acetate, and thereafter treating the resulting mixture with air having a relative humidity of 5 to 40 percent and preferably 10 to 30 percent in an electrostatic treatment zone.

By the process of the invention, the expensive costly foaming and filtering procedures of the wet mechanical processes are eliminated.

In contrast to the aforementioned procedureas de- 1 scribed in German Patent No. 1,078,961, the considerable costs for conditioning agents are avoided, as in the process of the invention, very inexpensive and readily available materials are used for conditioning agents. In the process of the invention, the plant is also considerably simplified.

As a result, a further cost savings is realized and additionally a higher degree of safety is ensured.

A further advantage of the invention lies in that after recovery of the kieserite, Sylvanite can be recovered without any further addition of conditioning agent to the crude salt. Still further the process has the advan tage that it utilizes essentially lower separation temperatures as a result of which a savings in energy costs are also realized.

The process of the invention will be further described in the following examples but the invention is in no wise to' be construed as limited thereby.

EXAMPLE 1 25 The examples, the results of which are set out in Table 1 represents the recovery of kieserite from a crude potassium salt containing about 12%- K 0 and about 28% kieserite, using a separation temperature of 35C, corresponding to 20% relative humidity of 7.5g I-l O/m air, absolute air'himidity, in a plate free fall separator. Following a single throughput, the following results were obtained:

TABLE 1 Ex. Conditioning g/t Kieser- Content Kieser- No. Agent ite resiite conc. due yield 2,4-dichlorophen- 300 26.1 25.5 15.1 oxy acetate (German Pat. 1,078,961) 2.

Silicic acid KS 404 200 Fatty acid C -C 150 26.6 24.1 14.8 3.

Fatty acid 150 17.5 30.7 C,,-C, 4.

Salicyclic acid 150 19.9 28.4 5.

ammonium acetate 100 fatty acid C -C 150 54.6 5.5 89.4 6.

ammonium formiate 100 fatty acid C -C 150 43.7 7.5 88.3 7.

ammonium acetate 100 salicyclic acid 150 53.5 5.3 90.0 8.

ammonium acetate 100 benzoic acid 150 55.1 5.0 90.4 9.

ammonium acetate 100 abietic acid 150 50.6 6.1 89.0

ammonium formiate 100 abietic acid 150 43.7 7.5 88.3

In the Table, column 1, of the table, shows the conditioning agent used, column 2, the kieserite content in the fraction, and column 3, the kieserite yield.

Examples 5 to 10 which correspond to the process of the invention, show a 20 to 30 percent higher preconcentrate than the comparison Examples 1-4. The kieserite yield in accordance with the invention amounts to from 70 to 75 percent higher than that obtained in Examples l-4.

The Examples in Table 2 show the recovery of kieserite recovered from a crude potassium salt containing 13.8% K 0 and 33.3% kieserite, the use of a separation temperature of between and 40C, corresponding to 10 to 40% relativehumidity in the warming air. The crude salt is treated with 150g/ton of a fatty acid having five to nine carbon atoms and l50g/t0n ammonium acetate. After a single throughput in the free fall separator, the following results were obtained:

In the Table, in the last column, the Kieserite portion in percentage is given, under which the amount of kieserite of a single throughput is to be understood, this therefore not being identical with the final yield of a continuous process. The kieserite remaining in the intermediate fraction, i.e., the differences to 100 percent are not shown in the Table. The technical advance of the process of the invention can be especially well seen from Examples 11-14 of Table 2. The separation can be carried out at or near room temperature.

Particularly good results are realized if in addition to the designated conditioning agent, the starting material is also treated with a water adsorption agent, as for instance, with a molecular sieve, disperse or granular silicic acid. It is then possible to increase the relative himidity in the warming air to about 50 percent, whereby a further temperature decrease of 5C can be realized.

The separation of kieserite from the preconcentrate succeeds particularly well according to the process of the invention when the latter is not further conditioned.

The Examples in Table 3 are directed to the recovery of kieserite from a crude potassium salt containing 13.3% K 0 and 26.1% kieserite at 30C, corresponding to a 25 percent relative humidity in the warming air, in the. free fall separator. The preconcentrate was separated once more without being further conditioned.

When 2,4-dichlorophenoxy acetate (Example 16) as described in German Pat. No. 1,078,961 was used at a relative humidity of 25 percent, no selective loading of the kieserite was obtained. The comparative Example 15 uses fatty acid (C -C Example 17 fatty acid and ammonium carbonate and Example 18 fatty acid and water containing soda and yield only kieserite concentrates containing 60 to 63% MgSO 'l-l O. Ammonium carbonate and sodium carbonate exert no influence on the separation yields of kieserite. The after concentrates of Examples 19-22 obtained in accordance with the process of the invention, show a 25 to 35 percent higher kieserite content than the after concentrates according to the comparison Examples.

TABLE III Ex. Conditioning g/t Kieserite Yield No. Agent preconafter 7:-

centrate conc.

fatty acid C -C 150 33.2 61.8 45.1 16.

2,4-dichlorophen- 300 26.1 17.5

oxy acetate (Ger. Pat. 1,078,961) 17.

ammonium carbonate fatty acid C -C 31.0 60.4 58.5 18.

sodium carbonate 100 fatty acid C,C 150 30.5 63.7 61.9 19.

ammonium acetate 100 fatty acid C -C 150 44.3 91.4 87.8 20.

ammonium acetate 100 O-cresotic acid 50 fatty acid C -C 100 52.7 94.2 86.9 21.

ammonium acetate 100 salicyclic acid 150 60.4 93.8 87.7 22.

ammonium formiate 100 benzoic acid 150 42.7 85.4 81.0

According to the process of the invention, kieserite can be recovered from hard salt (impure Sylvite) without first separating out the Sylvite and also from their residues. For carrying out the process of the invention, without further conditioning agents, there are necessary about 100g ammonium formiate or ammonium acetate per ton of residue.

The Examples of Table 4 represent the recovery of kieserite from hard salt residues that originate from a crude. salt electrostatic separation. For separating the midity of about 12 percent. The starting material had kieserite, the starting material is treated with 100g amthe following sieve analysis: monium acetate per ton of residue. The separation is I carried out at 15 to 40C in a plate free fall separator. larger than 0.5 4.0 0.25-0.5 64.0 0.16-O.25 16.6 TABLE IV I 0.1-0.16 7.3 smaller than 0.1 8.1

. TABLE VI Separation Kieserite Example Temp. rel. hustarting concen- Yield No. 0C. midity product trate 's CONTENT 1N PROPORTION IN '7. I concentrate residue concentrate residue 23. 40 10 70.4 95.2 85.7 CaF2 995 65g 913 81 caco. 0.2 0.7 30.0 70.0 25. 40 56.2 92.7 90.1 15 co 0 02 4 s10 0.2 33.7 4.3 95.7

These Examples show that already in a single separation stage a kieserite concentrate containing 92.7 to There was Obtained at the negative electrode, a 0

95% kieserite, i.e., a yield of 85.7 to 90.1% is realized. stantially' p liquid p (over 99 percent p li The kieserite yeild is, where a decreased tem was found to the extent of 95 percent in the residue and is utilized, even further improved. The techni l dwas separated off at the positive electrode. The yield of vance of the process of the invention is clearly to be highly pure liquid spar amounted to 91.3 percent. seen from the above Examples. We claim:

l. A process for the electrostatical separation of min- EXAMPLE 26 eral and salt mixtures which comprises rigorously mix- The product known as Magno (manufactured by ing the mineral or'salt mixture with a conditioning Magno Werk GM-Bl-l, Duisberg, Germany) containing agent said conditioning agent consisting essentially of 96.0% CaCO 1.1% MgCO 2.1% $20 and 0.8% a mixture of Fe O and A1 0 was treated with 100g first running A. a member selected from the group consisting of; fatty acid or with 100g O-cresotic acid and also with 30 a. aliphatic, unbranched fatty acids containing 100g technical ammonium acetate (Chemische Fabrik, three to 18 Carbon atoms. Lehrte, Germany) per ton of material to be worked. b. aromatic carboxylic acids, After warming in a drying oven to C, the resulting c. mixtures of said aliphatic and aromatic acids and mixture was separated in a free fall separator at 4 B. at least one ammonium salt of a lower aliphatic k/Vcm, at a relative air humidity of about 15%. 3 fattyacid The following results were obtained for a starting main the absence of a carrier therefor, and thereafter terial having the following particle size distribution: subjecting the resultant total mixture to treatment with air having a relative humidity of 5 to 40 percent in an electrostatic separation zone at a temw '7 large, than 0'5 40 perature from about 15 to 40C.

..Q.-Z .:9- 2. Process according to claim 1 wherein said aligjifgfiz 3:; phatic, unbranched fatty acid contains five to 12 carsmaller than 0.1 11.0 bon atoms.

TABLE V Run A Run B Proportion in Proportion in Content in percent Percent Content in percent percent Conc. Residue Conc. Residue Conc. Residue Conc. Residue CaCO 98.8 88.7 74.4 25.6 98.5 91.8 65.0 35.0 MgCO 1.0 3.0 1.0 2.7 SiO 0.1 7.0 3.3 96.7 0.2 4.6 5.5 94.5 Fe Oi+ A1503 .1 1 3 5.2 94.5 g .3 10 10.7 89.3

There were recovered at the negative electrode' a 3, P ss according to claim 1 wherein said ammoconcent ate of g y P CaCQa Of 985% The nium salt is a member selected from the group consist- MgCO is present 1n the concentrate as dolomite. The i f ammonium acetate d ammonium f i t f y mlnerals and z a 2 3 are Substan- 4. Process'according to claim 1 wherein said air has tially completely eliminated and are to be found only a l i humidity f 0 to 30 in the residue. 5. Process according to claim 1 wherein said ammonium salt is used in an amount of about 50 to about 200 EXAMPLE 27 g/ton of startmg salt or mineral mixture.

6. Process according to claim 1 wherein said salt or mineral mixture is the crude salt mixturederived in the A spar containing Cal CaCO recovery of potassium 0.03% Mg COa and 4.27% S -z w s treated With 1 g of 7. Process according to claim 6 which comprises sepa C5-C8 a y acid and g a ni m 806mm p n arating a kieserite concentrate from said crude salt of starting material and warmed n a drying e to mixture and thereafter recovering a Sylvanite concen- 50C. The electrostatic working up was carried out in irate f h remaining id -a plate free fall separator at 4 kV/cm and a relative hu- 1 1 =1= 1= 

2. Process according to claim 1 wherein said aliphatic, unbranched fatty acid contains five to 12 carbon atoms.
 3. Process according to claim 1 wherein said ammonium salt is a member selected from the group consisting of ammonium acetate and ammonium formiate.
 4. Process according to claim 1 wherein said air has a relative humidity of 10 to 30 percent.
 5. Process according to claim 1 wherein said ammonium salt is used in an amount of about 50 to about 200 g/ton of starting salt or mineral mixture.
 6. Process according to claim 1 wherein said salt or mineral mixture is the crude salt mixture derived in the recovery of potassium.
 7. Process according to claim 6 which comprises separating a kieserite concentrate from said crude salt mixture and thereafter recovering a Sylvanite concentrate from the remaining residue. 